"D1" Position

WARNING: This page is about a different car, the 2005 Nissan 350Z. However, it is still accessible from the selected car via links, so may be relevant.

The forward brake and the forward one-way clutch regulate reverse rotation of the mid sun gear.
The 1st one-way clutch regulates reverse rotation of the rear sun gear.
The 3rd one-way clutch regulates reverse rotation of the front sun gear.
During deceleration, the mid sun gear turns forward, so the forward one-way clutch idles and the engine brake is not activated.

Fig 1: Automatic Transmission Power Flow Diagram Position (D1)
Courtesy of NISSAN MOTOR CO., U.S.A.